1. Field of the Invention
The present invention relates to a thin film transistor array (TFT array). More particularly, the present invention relates to a transflective liquid crystal display (Transflective LCD) with high contrast ratio.
2. Description of Related Art
To match the life style of modern people, video or imaging equipment is becoming lighter and slimmer. Although the conventional cathode ray tube (CRT) has many advantages, the design of the electron gun renders it heavy and bulky. Moreover, there is always some risk of hurting viewer's eyes due to the production of some harmful radiation. With big leaps in the techniques in manufacturing semiconductor devices and opto-electronic devices, flat panel displays such as liquid crystal displays (LCD), organic light-emitting displays (OLED) and plasma display panels (PDP) has gradually become the mainstream display products.
According to the light source used, a liquid crystal display can be classified into three types: reflective LCD, transmissive LCD and transflective LCD. Taking a transflective LCD as an example, the transflective LCD mainly includes a transflective liquid crystal panel and a back light module. The transflective LCD panel includes a thin film transistor array, a color filter and a liquid crystal layer sandwiched therebetween. The back light module provides a surface light source to illuminate the transflective LCD panel for displaying images. More specifically, the thin film transistor array includes a plurality of pixels, each pixel has a transmissive region and a reflective region respectively, and wherein the thickness of liquid crystal layer located above the transmissive region is different from the thickness of liquid crystal layer located above the reflective region.
FIG. 1 is a schematic top view of a conventional transflective thin film transistor array. Referring FIG. 1, the conventional transflective thin film transistor array 100 includes a substrate (not shown), a plurality of scan lines 110 disposed on the substrate, a plurality of data lines 120 disposed on the substrate and a plurality of pixels 130 disposed on the substrate. Moreover, the conventional transflective thin film transistor array 100 further includes an alignment film (not shown) disposed over the substrate to cover the scan lines 110, the data lines 120 and the pixels 130.
As shown in FIG. 1, each pixel 130 includes a reflective region 132 and a transmissive region 134, wherein the transmissive region 134 is connected to and enclosed by the reflective region 132. A transition region (taper) 136 is formed between the reflective region 132 and the transmissive region 134 because different cell gaps are required in the reflective region 132 and the transmissive region 134. The profile of the transmissive region 134 is rectangle having a pair of long opposite sides L and a pair of short opposite sides S. It should be noted that, in the prior art, an included angle α between the long opposite side L or the short opposite side S of the transmissive region 134 and a rubbing direction R of the alignment film is about 45 degree. In other words, an included angle α between the extending direction of the transition region 136, which is parallel with the long opposite side L or the short opposite side S of the transmissive region 134, and a rubbing direction R of the alignment film is also about 45 degree. Due to the included angle α being about 45 degree, light leakage phenomenon occurs at the transition region 136. Therefore, contrast ratio of image displayed by a transflective LCD panel using the transflective thin film transistor array 100 is deteriorated. As described above, high definition transflective LCD panels having enhanced contrast ratio are required.